Steering wheels with driver airbag unit thus far developed include those to which the driver airbag unit is mounted on the driver-side face of the steering wheel, and configured to activate (blow) a horn when the driver airbag unit is pressed from the side of the driver and displaced away from the driver.
Patent Literature 1 (PTL 1: Japanese Unexamined Patent Application Publication No. 2006-218903) discloses a structure including a base plate that supports a driver airbag unit so as to move toward and away from the driver, the base plate being attached to the driver airbag unit on the opposite side of the driver, and attached to the steering wheel.
The driver airbag unit includes an airbag, an inflator for expanding the airbag, a retainer on which the airbag and the inflator are attached, and a module cover attached to the driver-side face of the retainer, so as to cover the folded body of the airbag. According to PTL 1, the retainer includes a guide shaft projecting from the retainer in a direction away from the driver. The base plate includes a guide shaft insertion hole, through which the guide shaft insertion hole is inserted so as to move toward and away from the driver. A flange larger in diameter than the guide shaft insertion hole is provided on an end portion of the guide shaft, to delimit the movement of the retainer away from the base plate. Coil springs are provided around the guide shaft, with an end portion abutted to the retainer and the other end portion abutted to the base plate. Accordingly, the driver airbag unit is biased toward the driver by the coil spring.
The base plate includes a bracket projecting in the direction away from the driver from the face of the base plate opposite to the driver, and upon connecting the bracket to the steering wheel the driver airbag unit is attached to the steering wheel via the base plate so as to move toward and away from the driver. A fixed contact of the horn switch is provided on the base plate, and a movable contact of the horn switch is provided on the retainer.
When the driver airbag unit is pressed from the side of the driver, the driver airbag unit is displaced toward the base plate along the guide shaft, and the movable contact on the side of the driver airbag unit is brought into contact with the fixed contact on the base plate, so that the horn is activated.